Exercise 3+ (Continuous integration)

[alessandrofelder]

Use CI to run the tests for you. (25 min)

Let's use Travis-ci to run our tests for every commit we push to our repository.

• Follow the guide provided by Travis for the general setup and the python instructions for testing this repository.
• Add .travis.yml to the repository, commit it and push it to GitHub. Link to this issue on that commit.